I have developed a relatively complete system for settling combat in roleplaying games.

Base HP: 5
Armor HP values:
0*: +0hp
1*: +1hp
2*: +2hp
3*: +3hp
4*: +4hp
5*: +5hp
Vitasuit/Vitacap/Ancient Plate: +6hp

Shield HP values:
0*: 1hp
1*: 1hp
2*: 2hp
3*: 3hp
4*: 4hp
5*: 5hp

Exceptions:
Stone Tortoise: 8hp
Omega Shell: 10hp

Shields regenerate 1hp per turn when not under attack for two turns. If broken, they do not begin regeneration for 5 turns.

Weapon damages and armor resistances work at a fairly constant rate, barring a few exceptions. Assuming that the armor and the weapon used to attack it are of equal star level, and the armor resists every inflicted damage type:

Gun dmg: 1
Hvy gun dmg: 2
Sword dmg: 2
Sword combo dmg: 3
Hvy sword dmg: 3
Hvy sword combo dmg: 4
Bomb dmg: 3
Hvy bomb dmg: 4

These values are reduced by 1 for every star level of defensive superiority, and are increased by 1 for every star level of defensive inferiority. Minimum damage is 0. The above values are increased by 1 when striking armor that resists half of the inflicted damage types, and increased by 2 when striking armor that doesn't resist the inflicted damage types at all.

Now for the list of exceptions:
*Ancient Plate, Ironmight Plate, and Volcanic Plate are immune to pure-normal weapon, and halve the damage of split-normal weapons.
*Azure Guardian, Ice Queen, Royal Jelly, Grey Feather, and Dread Skelly halve the damage of optimal pure-type weapons, and roughly quarter the damage of split-type weapons (rounded).
*Striker-line weapons deal gun damage, but can swing up to 6 times.
*Winmillion regular swings deal 1 damage, and each swing also fires a shot which deals 1 damage.
*Autogun-line attacks can either focus on a single character or on a group of them. If it focuses on one character, its shots cannot be dodged. If it focuses on a group of characters, it has a chance to hit all of them at once, but its shots can be dodged. Dodge mechanics will be explained later.

Each standard, non-combo, non-charge attack takes 1 turn to complete. Completing a combo will immobilize your character for an entire turn. Charge attacks without CTR will take 5 turns to charge up. Characters may approach, dodge, and kite while charging any weapon. These mechanics will be explained later. Bombers may only use charge attacks. Bombs will have a chance to hit every character in the immediate area. The default fuse time is 2 turns.

In the event of a tie, the defender wins.

Turns will proceed as follows:

Approach
In order for a swordsman (and bomber in some cases) to inflict damage, he must first get within attack range of the target. This is called "approach." The target isn't sitting still, however, so it takes some skill to successfully get within range. This is settled by two dicerolls:

1d6 approach roll for the attacker
*+1 for each level MSI
*-1 while charging a heavy weapon
*-2 while shielded
2d6 kite roll for the defender
*+1 for each MSI
*-1 if firing an immobilizing gun (like a Magnus)
*-1 while charging a gun or heavy weapon
*-1d6 while shielded

If the attacker gets within range, the next two dicerolls occur:

1d6 to hit
*+1 for each level of damage bonus
*+1 for fast bullets
1d6 to dodge
*+1 for each level MSI
*-2 while shielded (only if the character chooses to dodge while shielded)
*+1 if attacking from behind cover (can't be hit at all if the character is fully behind cover)
*-1 if attempting to dodge a heavy bomb or troika slam

If the defender chose to shield while dodging, then he must roll to determine whether he blocked in time to take the hit.

1d6 to block
*+1 for each level of relevant ASI (you don't get a bonus if you're wearing Justifier armor and you have a sword equipped)
*+1d6 if you don't attack at all this turn (automatic [i.e. no diceroll] block if you stay shielded through the next turn)

Charge attacks are handled differently for each weapon, but as a rule of thumb, each charge attack deals double the combo damage. I will list a few examples:

*The charge swing of a brandish deals 5 damage. The explosions in the trail each deal 1 damage per hit, for a maximum of 1d6 hits, modified by the star level of the weapon. The trail can hit targets at range.
*The Blitz Needle charge shots each deal 2 damage. Normal dodge rules still apply.
*The Troika slam deals 4 damage on the initial hit and 4 damage on the explosion. Alternate to-hit rules apply:
-first slam hits on a roll of 3+
-explosion cannot be dodged if the first slam hits
-if not hit by the first slam, the explosion can hit on a roll of 4+
*the stats of other unique weapons will be developed as the need or interest arises.

Some attacks deal statuses, and they must be handled appropriately.

slight, fair, moderate, good
minor, moderate, strong

*Slight chance: 6 on 1d6
*Fair chance: 5+ on 1d6
*Moderate chance: 4+ on 1d6
*Good chance: 3+ on 1d6
*Self-infliction: 1 on 1d6 (only on Faust/Gran Faust charge and Fang of Vog charge)

*Minor: +1 turns
*Moderate: +2 turns
*Strong: +3 turns

*Stun: halves approach, to-hit, and dodge rolls. Lasts 1d6 turns.
*Sleep: incapacitates the character and heals 0.5hp per turn. Lasts 2d6 turns.
*Curse: causes 1hp damage per attack. Lasts 2d6 turns.
*Poison: halves the effect of armor, halves weapon damage. Lasts 1d6 turns.
*Freeze: cannot approach, kite, or dodge for 1d6 turns. Deals 2hp damage upon thaw, or 3hp damage upon rapid thaw. Can be broken early for 0 damage.
*Shock: immobilizes the character for one turn upon any contact with the inflicting weapon. Deals 0.5hp damage.
*Fire: character takes 1hp damage per turn for 1d6 turns. Can be put out early with water.

Each bar of status resistance modifies the infliction chance by -1 and modifies the duration by -1 turns. Shields handle statuses differently:

*Stun: resistance allows the shield to cushion the impact, preventing involuntary movement. Lack of resistance allows the character to be thrown around when the shield is hit.
*Curse: lack of resistance prevents usage of the shield for the duration of the curse. Full resistance prevents the shield from being cursed.
*Poison: lack of resistance prevents shield regeneration for the duration of the status. Resistance modifies the duration of the poison by -1 turn per bar resistance. Full resistance allows the shield to regenerate normally.
*Freeze: If the shield breaks, lack of resistance will cause the shield to stay broken for 5+1d6 turns. Resistance modifies the effect of freeze by -1 turn per bar resistance. Full resistance allows the shield to regenerate after the normal 5 seconds of breakage.
*Shock: lack of resistance means that the shield will transfer the shock from the inflicting weapon to the shield's user. Resistance modifies the chance of infliction by -1 per bar resistance.
*Fire: lack of resistance will damage the shield by 1hp per turn for the duration of the fire. Resistance modifies the fire's duration by -1 turn per bar resistance, and modifies the infliction chance by -1 per bar resistance. Full resistance prevents the shield from catching fire at all.
*Sleep: your shield arm goes to sleep, and your shield stays forcibly raised for 1d6 turns.

Is all this too complicated?